A combustible cartridge case (CCC) typically includes two main structural components. The first is an elongated generally cylindrical combustible cartridge case body that has an interior area containing a propellant bed. The case body has a bottom dome portion to interface with a composite metal/elastomer case base. The second is an adapter with a tapered shoulder to interface with a projectile. The adapter can be manufactured from combustible materials or inert materials. The adapter and the body are affixed together by an adhesive at an angled lap-type joint known as a skive joint. The angled joining surfaces expose more material to the adhesive than a butt-type joint for greater structural strength.
The CCC configuration allows complex propellant bed geometries and integration with projectiles that have deep intrusions into the propellant bed (e.g., armor-piercing fin-stabilized discarding-sabot kinetic energy type projectiles). A typical assembly sequence includes assembling a projectile with an adapter, inverting the assembly to a nose-down orientation, and disposing a propellant bed to the intruding projectile. Meanwhile, the CCC body is assembled to a composite metal/elastomer case base. The base incorporates a cartridge head-spacing feature (e.g., a rim). Finally, the case base/CCC body assembly is attached to the projectile/adapter/propellant bed assembly at the skive joint with an adhesive.
The attachment of the case base/CCC body assembly to the projectile/adapter/propellant bed assembly is often used to establish and control the overall length of the complete cartridge. If the partially assembled cartridge needs to be shortened during manufacturing, the cartridge can be axially compressed so as to overdrive the skive joint, thereby shortening the overall length of the completed cartridge into an acceptable range. As a result, the overdriven skive joint forms a rear-facing lip as the adapter (female) expands beyond the CCC body (male), which creates a risk that the cartridge may be damaged. For example, sliding the complete cartridge across any discontinuity can cause the adapter lip be caught, torn, and possibly expose the propellant bed.